Light irradiation method, light irradiation device, and fine particle analyzing apparatus

Abstract

A light irradiation method of irradiating a specimen in a flow channel with directional light includes the step of irradiating the specimen with the directional light while performing scanning using the directional light in a widthwise direction of the flow channel. The directional light has an irradiation spot that is smaller than a width of the flow channel. Accordingly, energy density of the irradiation spot can be increased without increasing output power of a light source.

1. A light irradiation method of irradiating a specimen moving through a flow channel with directional light, the method comprising:
 irradiating the specimen with the directional light from a first light source while performing scanning using the directional light in a widthwise direction of the flow channel, the directional light having an at least substantially circular irradiation spot having a diameter that is smaller than a width of the flow channel, 
 obtaining positional information of the specimen prior to irradiating the specimen with the directional light by performing scanning of the specimen with a second irradiation spot from a second light source, and detecting a measurement light that is generated by the irradiation of the specimen by the second light source, 
 wherein irradiating the specimen with the directional light at a given time is based on the obtained positional information of the specimen, and 
 wherein scanning is performed in the widthwise direction of the flow channel at a single position in a flow channel direction a plurality of times during a period of time when the specimen moves through an area irradiated by the irradiation spot. 
 
     
     
       2. The method according to  claim 1 , wherein the scanning using the directional light is performed with at least any of a galvanometer, an electro-optical element, a polygon mirror, and an MEMS element. 
     
     
       3. The method according to  claim 1 , wherein the scanning using the directional light is performed under a condition satisfying the following Expression (1): 
       
         
           
             
               
                 
                   
                     
                       
                         D 
                         2 
                       
                       
                         v 
                         1 
                       
                     
                     > 
                     
                       
                         D 
                         1 
                       
                       
                         v 
                         2 
                       
                     
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         where v 1  is a speed of movement of the specimen in the interior of the flow channel, v 2  is a scanning speed of the directional light, D 1  is the width of the flow channel, and D 2  is a diameter of the irradiation spot. 
       
     
     
       4. A light irradiation device that irradiates a specimen moving through a flow channel with directional light, the device comprising at least:
 a first light source used to perform the irradiation with light having an at least substantially circular irradiation spot having a diameter that is smaller than a width of the flow channel; 
 a first scanning means for performing scanning using the light from the first light source in a widthwise direction of the flow channel, 
 a second light source; 
 a second scanning means for performing scanning of the specimen with a second irradiation spot from the second light source, and 
 a detector used to detect a measurement light that is generated by the irradiation of the specimen by the second light source, 
 wherein the measurement light is used to obtain positional information of the specimen prior to irradiating the specimen with the directional light; 
 wherein irradiating the specimen with the directional light at a given time is based on the obtained positional information of the specimen, and 
 wherein the first scanning means performs scanning in the widthwise direction of the flow channel at a single position in a flow channel direction a plurality of times during a period of time when the specimen moves through an area irradiated by the irradiation spot. 
 
     
     
       5. A fine particle analyzing apparatus comprising:
 the light irradiation device according to  claim 4 . 
 
     
     
       6. A light irradiation device that irradiates a specimen moving through a flow channel with directional light, the device comprising at least:
 a first light source used to perform the irradiation with light having an at least substantially circular irradiation spot having a diameter that is smaller than a width of the flow channel; 
 a first scanner that performs scanning using the light from the first light source in a widthwise direction of the flow channel, 
 a second light source; 
 a second scanner for performing scanning of the specimen with a second irradiation spot from the second light source, and 
 a detector used to detect a measurement light that is generated by the irradiation of the specimen by the second light source, 
 wherein the measurement light is used to obtain positional information of the specimen prior to irradiating the specimen with the directional light; 
 wherein irradiating the specimen with the directional light at a given time is based on the obtained positional information of the specimen, and 
 wherein the first scanner performs scanning in the widthwise direction of the flow channel at a single position in a flow channel direction a plurality of times during a period of time when the specimen moves through an area irradiated by the irradiation spot. 
 
     
     
       7. The method according to  claim 1 , wherein the substantially circular irradiation spot is larger than a size of the specimen. 
     
     
       8. The method according to  claim 1 , wherein the position information includes directional vectors of the specimen. 
     
     
       9. The method according to  claim 1 , wherein the scanning using the second light source is performed under a condition satisfying the following Expression (2): 
       
         
           
             
               
                 
                   
                     
                       
                         D 
                         4 
                       
                       
                         v 
                         1 
                       
                     
                     > 
                     
                       
                         D 
                         1 
                       
                       
                         v 
                         3 
                       
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
         where v 1  is the speed of movement of the specimen in the interior of the flow channel, v 3  is the scanning speed of light for obtaining positional information, D 1  is the width of the flow channel, and D 4  is the diameter of the second irradiation spot. 
       
     
     
       10. The method according to  claim 1 , wherein different positions in the flow channel direction and the widthwise direction of the flow channel are irradiated with the second irradiation spot to obtain the positional information. 
     
     
       11. The method according to  claim 1 , wherein the positional information includes position information in the widthwise direction of the flow channel, in the flow channel direction, and a depth direction that is orthogonal to the widthwise and flow channel directions. 
     
     
       12. The method according to  claim 1 , further comprising:
 obtaining positional information of the specimen subsequent to irradiating the specimen with the directional light by irradiating the specimen with light from a third light source. 
 
     
     
       13. The method according to  claim 12 , wherein obtaining positional information of the specimen subsequent to irradiating the specimen with the directional light includes:
 irradiating the specimen by performing scanning with a third irradiation spot from the third light source, and 
 detecting a measurement light that is generated by the irradiation of the specimen by the third light source. 
 
     
     
       14. The method according to  claim 13 , wherein different positions in the flow channel direction and the widthwise direction of the flow channel are irradiated with the third irradiation spot to obtain the positional information.